(1) Field of the Invention
The invention relates generally to the field of fiber optic data transmission systems and more particularly provides an arrangement for use in concurrently transmitting a plurality optical signals from a like plurality of inputs over a single optical fiber, and for separating the individual optical signals at the output.
(2) Description of the Prior Art
Fiber optic data transmission systems have been developed and are finding use in areas in which high data transfer rates are required, since optical fibers can easily transfer signals of very high bandwidth. In addition, fiber optic transmission systems are finding use in areas in which environmental damage can occur to conventional copper wire transmission systems. There are, however, several problems with use of optical fibers as data transmission media, which do not arise in connection with copper wire transmission system. One problem arises in connection with joining of two optical fibers, which must be accomplished if a single length of optical fiber does not sufficiently long to extend between the signal source and the intended destination. Joining of two copper wires in a conventional copper wire transmission system is generally a relatively simple matter. Another problem arises in connection with coupling of signals from a number of sources at a common location for transfer over a single optical fiber to a destination, and then separating the signals at the destination. With conventional copper wire transmission systems, it is well known that signals of diverse frequencies can easily be transferred over the same copper wire and resolved into the individual signals at the output.
A further problem arises if the source location and the destination need to rotate relative to each other, which may occur if the source is, for example, an optical signal generator located in a periscope and the destination is processing circuitry elsewhere in a submarine. It is known that optical fibers are generally quite brittle, and with twisting and bending they can easily be broken.
A prior art structure for coupling signals where the source location and the destination need to rotate relative to each other employs an intermediate de-rotation prism which must be rotated at one-half the rate of relative rotation of the source and destination. Such an arrangement clearly requires a complex mechanical linkage.